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Full text of "Text Book Of Mechanical Engineering"

Radius Link.                                249

a little piece filed out at the centre to admit the scriber. Lay
this template on the work, and trace out. Then drill the holes,
which are to be broached when all the parts are put together.
Remove all the outside material with a vertical milling tool having
a radius equal to that of the return curves, as shewn at c. The
inner slot may be cut out by one of three methods : (i) Let
several holes be drilled, as at c, one large enough to take a
slotting tool, and slot all round with hand feed ; (2) Drill a hole
to take a vertical milling tool, shewn at c, and a few more holes
to save the cutter, and mill out the rest, traversing by hand, first
one side and then the other ; (3) best of all, is the same as the
last, with this exception : the cutter is held in a special form of
vertical mill, called a 'profiling7 machine. Here the bearing
carrying the vertical spindle may be made to traverse any par-
ticular curve by applying to it a copy of the same shape, and its
action is thus similar to that of the copying lathe. The curve
would thus be finished right off without further filing ; and the
ends may be taken out with a double corner tool, then finished
by hand. The die (Fig. 242) is ultimately fitted to the link by
careful filing and scraping, and both link and die (after broaching
the former) are case-hardened. (See Appendices I. and II., pp. 752

XXVI.    Governor Pullies (Fig. 258). These are to be
machined as shewn upon the drawings.    The bosses are to be
bored by chucking in a dog-chuck, and the facing both of boss
and rim done at the same time.    Two settings are, of course,
necessary.    Next put the small pulley on a plain mandrel, and
the large pulley on an expanding mandrel, as shewn at page 155,
and turn the, rim surface in each case with parallel traverse :
then finish the curve with a hand tool.    The large pulley being in
halves must first be planed on its joint surface, as in the case of
the eccentric straps at Fig. 245, then drilled for the bolt-holes,
and bolted together for boring.   The keys are lastly t\ken out by
slotting,

XXVII.   Governor Bracket (Figs. 259-60). This is a
ratner more difficult example of lining out, but involves no new
principle, the only precaution of importance being very careful
levelling at every operation.   The casting is laid on its side, as in
the two views at B, and adjusted until tjie bush centres are of the